Hydrogenation reactor with improved flow distribution

ABSTRACT

A hydrogenation reactor comprises an elongated vertical container with a height greater than twice the width and divided into a plurality of tall slender chambers, either as a new reactor or as a modified existing reactor, having greatly increased distribution of a fluid reactant mixture flowing through a solid catalyst. Vertical baffles divide the container into various novel configurations having an increased height-towidth ratio giving increased linear velocity of the flowing reactants to several times that of the single pass reactor while maintaining the space velocity constant, the baffles further providing high strength-to-weight ratio and greater distribution while still permitting easy loading, regeneration, and dumping of the catalyst. With the last chamber being a downflow chamber in all modifications, catalyst &#39;&#39;&#39;&#39;carry over&#39;&#39;&#39;&#39; is minimized. Most of the modifications have an even number of chambers with inlet and exit nozzles at the bottoms of both the first chamber and last chamber insuring more efficient reverse flow at any time.

United States Patent 1 1 1111 3,902,856

Burroughs et a1. Sept. 2, 1975 [54] HYDROGENATION REACTOR WITH 3,484,214 12/1969 Gehring ct a1. 23/288 R MPROVED FLOW DISTRIBUTION 3,560,167 2/1971 Bruckner Ct a1, 23/288 R 3,598,539 8/1971 Pizzato 23/288 R [75] inventors: James W. Burroughs, Beaumont; 1 07900 9 1971 Bea] ct al, 23 23 R X Robert L. Herbst, Groves; William 3,652,451 3/1972 Boyd .1 23/288 R X C, Moyer, Port Arthur; Jesse M 3,702,238 11/1972 Armistead Ct a1 23/288 R Gray, Jr., Houston, all of Tex. Primary ExaminerBarry S. Richman [73] Asslgnee: Texaco New York Attorney, Agent, or FirmT. H. Whaley; C. G. Ries; [22] Filed: Nov. 14, 1973 Theron H. Nichols 211 Appl. No; 415,718 [57] ABSTRACT Related Application Data A hydrogenation reactor comprises an elongated verti- [62] Division of Ser. No. 186,638, Oct. 5, 1971, cal container with a height greater than twice the abandoned. width and divided into a plurality of tall slender chambers, either as a new reactor or as a modified existing 1 Cl 23/288 23/238 reactor, having greatly increased distribution of a fluid 08/ 146 reactant mixture flowing through a solid catalyst. Ver- 1 lIllj g 23/16 tical baffles divide the container into various novel [58] Field of Search 23/288 R, 288 A, 288 E; configurations having an increased height-to-width 208/5 146 ratio giving increased linear velocity of the flowing reactants to several times that of the single pass reactor [56] References Cited while maintaining the space velocity constant, the baf- UNlTED STATES PATENTS fles further providing high strength-to-weight ratio and 1 036,610 8/1912 Grosvcnor 23/288 E x greater distribution while} Permitting easy W 2:106,735 2/1938 Gwynn 208/57 x regeneratlon and dumpmg of the catalyst Wlth the 2,127,561 8/1938 Herrmann 23/288 R last Chamber being a downflow chamber in all modifi- 2,472,254 6/1949 Johnson 23/288 R X cations, catalyst carry over" is minimized. Most of 2,835,560 5/1958 Bason et al. 23/288 R the modifications have an even number of chambers 3,142,545 7/1 Raarup cl 23/288 R with inlet and exit nozzles at the bottoms of both the 312161951 11/ 1965 Erickson 23/285 X first chamber and last chamber insuring more efficient 3,368,875 2/1968 Tullencrs 23/288 E reverse flow at any time 3,423,176 1/1969 Kabisch et a1 23/288 E X 3,449,099 6/1969 "llaylor ct a1 23/288R X 1 Claim, 14 Drawing Figures PATENTEUSEP ems 3.902.856

sum 3 0 1 PATENTED EP 2 tYs saw u UF 4 HYDROGENATION REACTOR WITH IMPROVED FLOW DISTRIBUTION. This is a division of application Scr. No. 186.638, filed Oct. 5, I97] and now abandoned.

OBJECTS OF THE INVENTION A primary object of this invention -is to provide a hydrogenation reactor having a fluid reactant mixture with a solid catalyst that provides increased distribution of the fluid reactant mixture flowing through the solid catalyst.

Another primary object of this invention is to provide a hydrogenation reactor that has a height of over twice the width resulting in greatly increased distribution of a solid catalyst in a liquid reactant, produces greater contact between the liquid reactant and the catalyst, and channelizing is prevented.

Another object of this invention is to provide a hydrogenation reactor which has increased distribution while still permitting easy loading, regeneration, and dumping of the catalyst.

A further object of this invention is to provide a hydrogenation reactor which may be modified with baffles for increasing the distribution of the fluid reactant mixture and yet increase the strength-to-weight ratio.

A still further object of this invention is to provide a hydrogenation reactor which has an efficient reverse flow operation at any time.

Another object of this invention is to provide a hydrogenation reactor that provides increased linear velocity while maintaining a constant space velocity.

Yet another object of this invention is to provide a hydrogenation reactor that is easy to operate and is of simple configuration and economical to form and assemble.

Other objects and various advantages of the disclosed hydrogenation reactor with improved flow distribution will be apparent from the following detailed description together with the accompanying drawings, submitted for purposes of illustration only and not intended to define the scope of invention, reference being had for that purpose to the subjoined claims.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings diagrammatically illustrate by way of example, not by way of limitation, several forms of the invention wherein like reference numerals designate corresponding parts in the several views in which:

FIG. 1 illustrates schematically one modification of the invention, with parts in section for clarity of disclosure, comprising a vertical elongated container having one baffle therein;

, FIG. 2 is a section at 2-2 on FIG. 1;

FIG. 3 is a schematic sectional view of another elongated vertical chambered hydrogenation reactor;

FIG. 4 illustrates schematically a sectional view of another modification of the reactor of FIG. 1;

FIG. 5 is a section at 5-5 of FIG. 4;

FIG. 6 is a perspective view, schematically illustrated. of the inner chamber of the reactor of FIG. 4;

FIG. 7 is a schematic view showing the assembly of the cylindrical chamber of FIG. 6;

FIG. 8 illustrates schematically'a view of another modification of the reactor of FIG. I with'another cylindrical baffle positioned inside an elongated cylindrical container, with parts illustrated in section;

FIG. 9 is a sectional view at 99 on FIG. 8;

FIG. I0 is a sectional view at I0-I0 on FIG. 8;

FIG. I] is a perspective view of the inner cylindrical chamber of FIG. 8 with parts removed for clarity of disclosure;

FIG. l2 is a schematic sectional view of another modification of the hydrogenation reactor of FIG. 1;

FIG. 13 is a sectional view at l3-I3 on FIG. I2; and

FIG. 14 is a modification of FIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention disclosed herein the scope of which being defined in the appended claims is not limited in its application to the details of construction and arrangement of parts shown and described, since the invention is capable of other embodiments and of being practiced or carried out in various other ways. Also it is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation.

FIG. 1 shows an improved liquid distribution in a hydrogenation reactor 10a, the reactor container configuration Ilu which allows a combination of upflow and downflow operation of a fluid reactant mixture 12, as a charge oil and hydrogen flowing through a mass of solid catalyst pellets 13 as illustrated. These pellets may be of any shape and size, such as but not limited to, cylindrical pellets from 1/16 inch to 1 inch in length. This reactor 10 is bisected with an elongated vertical baffle 14. The baffle has a fluid tight connection with the bottom of the container Ila forming a first elongated vertical chamber 15 with an inlet nozzle 16a in the bottom and to one side of the baffle, the nozzle having a perforated cover or a screen (not shown) and being covered with a layer of mullite balls 17 or slag which acts as a filter and retains the catalyst in the reactor. The fluid reactant 12 comprising hydrogen with components in oil and catalyst 13 mixture fill the cylindrical container 11 on both sides of the baffle 14. An outlet nozzle 18a is positioned on the other side of the baffle from the inlet nozzle 16a at the bottom of the second chamber 19 formed by dividing vertical baffle. Likewise, outlet nozzle 18a is covered with a perforated cover or screen (not shown) and a layer of mullite balls 17 or slag that acts as a filter or catalyst retainer. While only one baffle is illustrated and described in this embodiment, a plurality of baffles may be utilized if so required for increased distribution of the fluid reactants. This baffle or these baffles provide at least two-pass flow, or more, in the reactor.

Another critical feature of this reactor is that the height of the totalcontainer I1 is over twice the width or diameter ofthe container. Thus, in operation charge oil and hydrogen enter at the bottom of the first chamber 15 of the reactor flow upward and over the baffle l4 and then downward to the outlet IS on the opposite side of the baffle. This results in greatly increased distribution of the catalyst in the reactants, provides greater contact between the liquid reactant and the solid catalyst, and prevents channelizing.

This modification of the reactor improves liquid distribution in two ways: l the liquid distribution is optimum on the upflow side, since this side of the reactor should have a continuous liquid phase with a minimum of channelizing. and (2) liquid distribution is improved on the downflow side since the cross section flow area is one-half or more that of the normal reactor.

The catalyst 13 is filled to the top of the reactor to minimize agitation due to upflow operation. Some catalyst attrition is inherent in upflow operation and can result in excessive catalyst carry over; however, the novel configuration of the modified reactor provides upflow followed by downflow operation which permits the catalyst in the downflow side to act as a filter for the catalyst from the upflow chamber. Accordingly an opti mum liquid distribution results in the upflow chamber with less catalyst carry over from the reactor than from a reactor with only upflow operation.

The symmetrical design of the reactor permits efficient reverse flow operation at any time. This feature allows efficient operations to be quickly restored in the event of pressure drop buildup or channelizing in the downflow chamber.

Preferably, the vertical elongated container and baffie are formed of an alloy or is alloy-lined to protect them from hydrogen attack.

In addition to the above advantages, contacting in the reactor bed is improved, since linear velocity in the bed is doubled, at least, and catalyst carry over is no greater than for normal downflow of reactors.

FIG. 2, a sectional view of FIG. 1, illustrates how the baffle divides the overall container into two chambers 15 and 19.

FIG. 3 illustrates another embodiment 10b comprising an even number of elongated vertical chambers a to 20f. These chambers are serially interconnected with passage means 21a to 21:: for each respective pair of adjacent chambers. The first chamber 20:: has its inlet nozzle 16b at the bottom of chamber 200 and the last chamber 20f has its cxit nozzle 18/2 at the bottom of chamber 20fwhich like most of the other modifications disclosed provides efficient reverse flow at any time. The first chamber 20a has a passage 2111 at the top thereof turning through 180 to connect to the top of the second chamber 20b. The second chamber 2012 has a passage 21b at its bottom to connect, after turning 180, to the third slender elongated vertical chamber 200. Chambers 200 and 20d are interconnected at the tops of each with a passage 21c and chambers 20d and 20e are interconnected at their bottoms with a 180 angled passage 21d. The last two chambers illustrated, chambers 202 and 20f, are interconnected at the tops of each with a passage 21e thereby allowing outflow at the exit nozzle 18b at the bottom of the last passage 21f. The number of elongated vertical passages is preferably an even number in order to provide an upflow chamber as the first chamber and a downflow chamber as the last chamber to insure efficient reverse flow at any time without loss of catalyst. As clearly shown in FIG. 3, the chambers have equal cross-sectional areas and each of the U-bend angles has a cross-sectional area equal to that of the chambers.

Filter-screens 22a and 22f are provided at the top of each U-bend angle to prevent catalyst movement or carry over from one vertical chamber to the next. Catalyst fills all the vertical chambers. Filters such as ceramic balls 17 are positioned at the inlet and outlet and in angled passages 21b and 21:1 for forming filterscreens and for improved flow distribution in the hydrogenation reactor. Each of the elongated serially interconnected vertical chambers is spaced from the others for increased cooling therebetween.

FIGS. 47 illustrate another modification of the invention. FIG. 5, a cross sectional view of the modified reactor of FIG. 4, illustrates an elongated vertical outer housing forming a container with an elongated vertical tube inside thereof forming inner chamber 23 which is coaxial and concentric therewith outer annular chamber Ilt'. The inner chamber 23 is connected at the bottom to the outer container 110, and secured around the periphery thereof are one or more inlet nozzles'l6tz'Likewise, filters 17 are positioned around the inlets. A catalyst 13 fills the two containers. An exit nozzle 18c is positioned in the bottom of inner container 23 with filter l7 thereover for preventing outflow of the catalyst with the reactants. In the center of this modified reactor at the bottom is the exit nozzle 18: with filter l7 therewith.

In operation, fluid reactants enter at the bottom and flow around the outer peripheral annular chamber 11c, over the top of the inner chamber, and down the inside cylindrical chamber 23 to flow out the exit nozzle 180. This inner chamber 23 may be a prefabricated cylinder formed of staves 24 which may be dismantled, and then reassembled inside the reactor and pulled together with circumscribing straps 25. While only two inlet nozzles are illustrated, a multiplicity of inlet nozzles may be positioned around the peripheral of the outer annular chamber. The plurality of inlet nozzles provides uniform distribution of the charge entry. For reverse flow operation the feed is introduced into the bottom of the central chamber so that flow would be upward through the cylindrical chamber and downward through the annular outer chamber. While the cross sectional area of the outer and inner chambers may be equal, likewise they may also be varied to optimize flow distribution.

Catalyst is filled to the top of the reactor to minimize agitation of catalyst due to upflow operations.

FIG. 5 a sectional view of FIG. 4 illustrates the relative area of the two chambers.

FIG. 6 illustrates the inner cylindrical chamber 23 as being formed of staves 24 which are reassembled and secured with the straps 25 inside the outer chamber.

FIG. 7 illustrates the assembly of the inner cylindrical chamber comprising the insertion of staves 24 internally of the outer chamber llc.

FIGS. 8-11 illustrate another modification of the reactor l0d which provides the advantages of increasing the linear velocity of the flowing medium'in the reactor to several times that of the single pass reactor of a given diameter. Space velocity (volume of oil per hour per volume of linear catalyst) would remain unchanged. In this reactor, formed basically of an elongated vertical container 11d having a height greater than twice the width or diameter includes an inner cylinder 26, for forming a cylindrical inner chamber, the cylinder being attached to the bottom of the outer container 1 Id. The inner cylinder 26 as shown in FIGS. 8, l0 and 11, comprises two semicylindrical walls 27 and 28, and has an opening 29 in wall 27.

With cylinder 26 concentrically positioned inside of container lld, FIG. 8, an annulus is formed therebetween. This annulus is cut into two semiannular chambers 30 and 31 by vertical plates 32 and 33, FIG. 11, extending from cylinder 26 at the joint between walls 27 and 28 to the walls of the container 11d, FIG. 10, and by arcuate plate 34, FIG. 11, extending from the top edgesof wall 27 and the flat plates 32 and 33 to the container 1 Id, FIG. 8. A suitable catalyst fills all chambers.

. Thus in operation, flow the reactant passes from inlet 16d down through semiannular chamber 30,

through opening 29, up through cylinder 26 and over into thesemi-annular chamber 31, down the chamber and out the bottom exit nozzle 18d.

The embodiment of FIG. 9 is easy to design and install. In this modification which comprises only three chambers, the inner sectional area of the cylindrical chamber is one-third the total area whereby the other two semiannular chambers are one-third each in area. The advantages of this modification are: (1) vertical baffling is relatively simple and inexpensive in increasing the height-to-diameter ratio of the reactor; (2) the flat plates support the inner cylindrical section and thereby strengthen the overall structure of the reactor; (3) the flow of oil and hydrogen through the reactor can be reversed during the operation at any time; (4) all sections can be regenerated in the regular manner and the catalyst may be dumped through nozzles in the bottom; and (5) the internal baffles may be made from low alloy steel and accordingly would not need to be alloy clad.

FIGS. 12 to 14 disclose another embodiment of the hydrogenation reactor IOe, FIG. 12, which like all embodiments except that of FIG. 8, includes an even number of chambers. These chambers are elongated and vertical, and like all other modifications, have a height over twice the width. This reactor 100 comprises an odd number of chambers around a central cylindrical chamber. In the exemplementary illustration seven chambers 35 to 41, FIG. 13, are formed around one cylindrical chamber 42 whereby the inlet nozzle l6e is formed in the bottom of the first chamber 35 which is one of seven around the periphery of the inner chamber 42. Each pair of adjacent chambers is interconnected with the passages. The first chamber 35 being an upflow chamber has its outlet and passage at the top which connects with its adjacent chamber 36 at its top, this second chamber being a downflow chamber. The second and third adjacent chambers 36 and 37, respectively, are interconnected at the bottoms thereof. The next two chambers, 37 and 38, the third and fourth chambers, are interconnected at the top thereof whereby with an odd number of peripheral chambers around the periphery of inner chamber 42 the last or add numbered chamber, the seventh or chamber 41 in this case is an upflow chamber. This last upflow chamber 41 is connected with a passage at its top to the top of the center and last downflow chamber 42, whereby flow passes out of the bottom of the chamber and out of the exit nozzle l8e therein. Both entrance and exit nozzles have a filter l7 thereover as illustrated by the mullite balls.

While the chambers illustrated in FIG. 13 have straight solid adjacent walls 43 to 49 therebetween, the walls 50 to 56 illustrated in the FIG. 14 embodiment are made up of two walls each joined at their adjacent edges. In this arrangement the seven elongated vertical chambers form the annular space around the center heptagonal chamber. All chambers have an equal cross sectional area. With the first and last chamber being formed as an upflow and downflow chamber, respectively, reverse flow through the reactor may be efficiently accomplished and whenever desired catalyst.

carry over is minimized since the last chamber is always a downfall chamber. The baffles are either welded or bolted into position.

Likewise, these modifications provide increased linear velocity with improved distribution of the flowing stream throughout the reactor catalyst bed and therefore provide an improved and more efficient reactor in terms of oil throughput, i.e., throughput rate'and total throughput (barrels of oil per pound of catalyst). Likewise the quality of the hydrogen treated oil is improved with respect to initial color, color stability, thermal, and oxidation stability.

While only a few embodiments of the invention have been shown in the accompanying drawings, it will be evident that various other modifications are possible in the arrangement and construction of the hydrogenation reactor with improved fluid distribution, without departing from the scope of the invention.

We claim:

1. A hydrogenation reactor for catalytically hydrogenating a reactant mixture with a catalyst comprising,

a. elongated means forming a plurality of an even number and of at least six separate elongated vertical chambers, each said chamber having upper and lower ends and the cross-sectional areas of all of said vertical chambers being equal,

b. a first filter means in said upper end of each elongated vertical chamber and a second filter means in said lower end of each elongated vertical chamber, each said second filter means comprising a bed of ceramic balls, for preventing carryover of the catalysts,

c. a bed of particulate catalyst at least partially filling each of said chambers, each said bed of catalyst being supported on each respective bed of ceramic balls within said chamber,

d, detachable first U-shaped passage means serially interconnecting said upper ends of consecutive separate chambers comprising the first and second chambers, the third and fourth chambers and the fifth and sixth chambers and subsequent oddnumbered and adjacent downstream evennumbered chambers for passing all of the fluid reactant mixture through each of said separate chambers,

e. detachable second U-shaped passage means serially interconnecting said lower ends of consecutive pairs of separate chambers comprising the second and third chambers and the fourth and fifth chambers and subsequent even-numbered and adjacent downstream odd-numbered chambers for passing all of the fluid reactant mixture through each of said separate chambers, L

f. all of said detachable U-shaped passage mea lfs having cross-sectional areas equal to the crosssectional area of said chambers,

g. inlet means in the lower end of the first of said elongated vertical chambers for injecting a fluid reactant mixture into said reactor, said inlet means including a first ceramic ball bed retaining means for supporting said bed of ceramic balls in said first chamber and preventing the passage of said ceramic balls and said particulate catalyst supported thereon out of said reactor and h. outlet means in the lower end of the last of said elongated vertical chambers for removing reaction products from said reactor, said outlet means including a second ceramic ball bed retaining means for supporting said bed of ceramic balls in said last of said chambers and preventing the passage of said ceramic balls and said particulate catalyst supported thereon out of said reactor,

. whereby said serially interconnected configuration forms an improved reactor having simplicity of construction, simplicity of maintenance by easy replacement of individual vertical chambers. ease of increasing and decreasing of size, ease of catalyst 

1. A HYDROGENATION REACTOR FOR CATALYTICALLY HYDROGENATING A REACTANT MIXTURE WITH A CATALYST COMPRISING. A. ELONGATED MEANS FORMING A PLURALITY OF AN EVEN NUMBER AND OF AT LEAST SIX SEPARATE ELONATED VERTICAL CHAMBERS, EACH SAID CHAMBER HAVING UPPR AND LOWER ENDS AND THE CROSS-SECTIONAL AREAS OF ALL OF SAID VERTICAL CHAMBERS BEING EQUAL, B. A FIRST FILTER MEANS IN SAID UPPER END OF EACH ELONGATED VERTICAL CHAMBER AND A SECOND FILTER MEANS IN SAID SECOND END OF EACH ELONGATED VERTICAL CHAMBER, EACH SAID SECOND FILTER MEANS COMPRISING A BED OF CERAMIC OF BALLS, FOR PREVENTING CARRYOVER OF THE CATALYSTS, C. A BED OF PARTICULATE CATALYST AT LEAST PARTIALLY FILLING EACH OF SAID CHAMBERS, EACH SAID BED OF CATALYST BEING SUPPORTED ON EACH RESPECTIVE BED OF CREAMIC BALLS WITHIN SAID CHAMBER, D. DETACHABLE FIRST U-SHAPED PASSAGE MEANS SERIALLY INTERCONNECTING SAID UPPER ENDS OF CONSECUTIVE SEPARATE CHAMBERS COMPRISING THE FIRST AND SECOND CHAMBERS, THE THIRD AND FORTH CHAMBERS AND THE FIFTH AND SIXTH CHAMBERS AND SUBSEQUENT ODD-NUMBERED AND ADJACANT DOWNSTREAM EVEN-NUMBERED CHAMBERS FOR PASSING ALL OF THE FLUID REACTANT MIXTURE THROUGH EACH OF SAID SEPARATE CHAMBERS, E. DETACHABLE SECOND U-SHAPED PASSAGE MEANS SERIALLY INTERCONNECTING SAID LOWER ENDS OF CONSTRUCTIVE PAIRS OF SEPARATE CHAMBERS COMPRISING THE SECOND AND THIRD CHAMBERS AND THE FOURTH AND FIFTH CHAMBERS AND SUBSEQUENT EVENNUMBERED AND ADJACENT DOWNSTREAM ODD-NUMBERED CHAMBERS FOR PASSING ALL OF THE FLUID REACTANT MIXTURE THROUGH EACH OF SAID SEPARATE CHAMBERS, F. ALLL OF SAID DETACHABLE U-SHAPED PASSAGE MEANS HAVING CROSS-SECTTIONAL AREAS TO THE CROSS-SECTIONAL AREA OF SAID CHAMBERS, G. INLET MEANS IN THE LOWER END OF THE FIRST OF SAID ELONGATED VERTICAL CHAMBERS FOR INJECTING A FLUID REACTANT MIXTURE INTO SAID REACTOR, SAID INLET MEANS INCLUDING A FIRST CERAMIC BALL BED RETAINING MEANS FOR SUPPORTING SAID BED OF CERAMIC BALLS IN SAID FIRST CHAMBER AND PREVENTING THE PASSAGE OF SAID CREAMIC BALLS AND SAID PARTICULATE CATALYST SUPPOSTED THEREON OUT OF SAID REACTOR AND H. OUTLET MEANS IN THE LOWER END OF THE LAST OF SAID ELONGATED VERTICAL CHAMBERS FOR REMOVING REACTION PRODUCTS FROM SAID REACTOR, SAID OUTLET MEANS INCLUDING A SECOND CERAMIC BALL BED RETAINING MEANS FOR SUPPORTING SAID BED OF CERAMIC BALLS IN SAID LAST OF SAID CHAMBERS AND PREVENTING THE PASSAGE OF SAID CERAMIC BALLS AND SAID PARTICULATE CATALYST SUPPORTED THEREON OUT OF SAID REACTOR. I. WHEREBY SAID SERIALLY INTERCONNECTED CONFIGURATION FORMS AN IMPROVED REACTOR HAVING SIMPLICITY OF CONSTRUCTION, SIMPLICITY OF MAINTENANCE BY EASY REPLACEMENT OF INDIVIDUAL VERTICAL CHAMBERS, EASE OF INCREASING AND DECREASING OF SIZE, EASE OF CATALYST LOADING AND UNLOADING, IMPROVED AND INFINITE CONTACT BETWEEN THE FLUID REACTANT MIXTURE AND THE PARTICULATE CATALYST, AND INSURANCE OF EFFICIENT REVERSE FLOW CAPABILITIES AT ANY TIME WITHOUT LOSS OF CATALYST BY CARRYOVER. 